1. Field of the Invention
This invention relates in general to antilock braking system and in particular continuous and adaptive anti-lock braking systems.
2. Description of the Related Art
Present day vehicle braking systems typically include secondary braking systems such as anti-lock braking (ABS), traction control (TC), and vehicle stability control (VSC) functions. Sensors provide input signals to an electronic control unit (ECU) concerning the vehicles velocity in addition to wheel slip and/or trajectory changes. The ECU provides output command signals to electrically activated devices to apply, hold, and relieve (dump) hydraulic braking to/from the vehicle brakes for applying, maintaining, or relieving pressure at respective brake actuators of each wheel of the vehicle. Such valves are independently actuated to control the vehicle braking at a respective wheel.
During secondary braking operations, the braking control system controls the applied braking force to the vehicle by pulsating (modulating) the braking force applied to each wheel via the electrically activated devices. ABS systems, for example, rapidly apply and release a respective brake actuator to rapidly decelerate the vehicle in an efficient manner. Such braking functionality is well known to those skilled in the art. The objective is to decelerate the vehicle rapidly without locking up each vehicle wheel while maintaining a directional path of travel along the vehicle's intended trajectory path. Typically this is achieved by monitoring vehicle speed and wheel slip at each wheel and applying an ABS braking control strategy. The braking control strategy uses a predetermined ABS control algorithm based on the vehicle speed and wheel speed differentials.
Typically, the braking control strategy will factor in only wheel slip and vehicle speed parameters for rapidly decelerating the vehicle or bringing the vehicle to a stop utilizing ABS control. Factors not taken into consideration are objects within a vehicles intended trajectory or adjacent the vehicle and their respective distances from the driven vehicle. Applying a braking strategy for minimizing the stopping distance in all cases could compromise vehicle stability and lead to a collision with adjacent vehicles. Alternatively applying a braking strategy for maintaining full vehicle stability may not allow the operator to stop the vehicle in the distance available.